| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 40 |
| 3 | 277 |
| 4 | 1935 |
| 5 | 13540 |
| 6 | 94774 |
| 7 | 663411 |
| 8 | 4643869 |
| 9 | 32507074 |
| 10 | 227549508 |
| 11 | 1592846545 |
| 12 | 11149925803 |
| 13 | 78049480608 |
| 14 | 546346364242 |
| 15 | 3824424549679 |
| 16 | 26770971847737 |
| 17 | 187396802934142 |
| 18 | 1311777620538976 |
| 19 | 9182443343772813 |
[1,6,40,277,1935,13540,94774,663411,4643869, 32507074,227549508,1592846545,11149925803, 78049480608,546346364242,3824424549679, 26770971847737,187396802934142,1311777620538976, 9182443343772813] |